Method and system for compressing location data of a radio for over-the-air transmission

ABSTRACT

Disclosed are methods and systems for compressing location data of a radio for over-the-air transmission. A method includes obtaining raw latitude and raw longitude coordinates reflecting a current location of the client device, the raw latitude coordinate represented by x number of bits and the raw longitude coordinate represented by y number of bits. The raw latitude coordinate is truncated by removing n number of most significant bits from the raw latitude coordinate to create a compressed latitude coordinate. The raw longitude coordinate is truncated by removing m number of most significant bits from the raw longitude coordinate to create a compressed longitude coordinate, where m varies as a function of the value of the raw latitude coordinate. The compressed longitude and compressed latitude coordinates are then transmitted to another network device for decompression and use as an indication of the client device&#39;s absolute location.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to communication systems andmore particularly to a method for compressing location data, such as GPSdata, for transmission over the air to another network communicationsdevice, where it can be decompressed.

BACKGROUND

Mobile cell telephones, two-way radios, and other wireless clientdevices (WCDs) are experiencing tremendous growth in the U.S. and aroundthe globe, giving users the ability to place a call, including anemergency call, from almost anywhere at any time. One important featurethat is being included in most modern WCDs is an ability to determineand report a current location of the WCD.

Various methods to locate a WCD, at least approximately, may be used.One known approach to determine the location of a WCD is ground-basedtriangulation. In a ground-based triangulation system, the WCD'slocation is identified through a ranging technique between a pluralityof base stations and a transponder at the WCD.

Another known technique is based on a determined time difference ofarrival (TDOA) in which a data burst is received simultaneously at threebase station sites. From the time difference of arrival of the databurst from the WCD at each of the base station sites, the approximatelocation of the WCD can be determined.

In a third known technique, a Global Positioning System (GPS) ofsatellites and a corresponding receiver in the WCD may be used. GPS ismade up of more than two dozen earth-orbiting GPS satellites. Eachsatellite contains a computer, an atomic clock, and a radio. Eachsatellite continually broadcasts its changing position and time. Theseprecise timing and position signals broadcast in radio frequency, allowthe GPS receiver in the WCD to accurately determine a location of theGPS receiver (longitude, latitude, and/or altitude) anywhere on Earththat has a direct or indirect view of the orbiting satellites. The GPSsatellites are positioned in orbit in a manner such that from any givenpoint on Earth, at least four GPS satellites are visible above thehorizon at any one time. The GPS receiver in the WCD also contains itsown receiver and a computer that calculates its position using a processcalled trilateration, which is similar to triangulation. The GPSreceiver calculates time signals from at least three GPS satellites tomeasure its distance from each satellite and to calculate a result. Thecalculation result is provided in the form of a geographic position(longitude and latitude). The location accuracy may be anywhere from 1to 100 meters depending on the type of equipment used and the number ofsatellites visible. The GPS is owned and operated by the U.S. Departmentof Defense, but is available for general use around the world. TheEuropean Space Agency and the European Union are also building out aseparate global navigation satellite system called Galileo, among otheradditional projects being pursued by other countries.

In one example, the GPS data payload, used to provide other devices withthe determined position of the WCD, may use a 32-bit long absolutelatitude coordinate and a 32-bit long absolute longitude coordinate.Given the frequency of location updates, and the number of WCDstransmitting location updates, the transfer of 64-bits of location data,in addition to overhead required to transfer the 64-bits of raw locationdata, generates significant traffic over a wireless network. Forexample, using the Motorola Solutions™ MOTOTRBO Location Request andResponse Protocol (LRRP), in which LRRP control and data messages aresent via a wireless radio network within UDP/IP packets that aretransported over the common air interface (CAI), 6-7 LRRP transmissionbursts may be required to transfer the 64-bits of raw location data,including overhead, taking up more than 300 ms of transmit time perupdate.

Clearly, as more and more devices implement GPS receivers and locationreporting, and as the frequency of location updates increases, GPSpayload data is becoming a predominant bandwidth consumer over wirelessarea networks.

What is needed is a method and system for more efficiently transmittingGPS payload data, so that useful location-based services can continue tobe provided and locations of WCD's provided to those agencies that relyon them, while decreasing the costs and network utilization ratesinherent in providing such services.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying figures, where like reference numerals refer toidentical or functionally similar elements throughout the separateviews, together with the detailed description below, are incorporated inand form part of the specification, and serve to further illustrateembodiments of concepts that include the claimed invention, and explainvarious principles and advantages of those embodiments.

FIG. 1 is a block diagram of a communication system employing a methodand system for compressing and decompressing location data of a radiofor over-the-air transmission.

FIG. 2 is a block diagram illustrating further detail of a client deviceand wireless communications device employed in the communication systemshown in FIG. 1.

FIG. 3 illustrates an example location payload packet format includingcompressed location coordinates for transmission between a client deviceand a wireless communications device employed in the communicationsystem shown in FIG. 1.

FIG. 4 is a flow chart illustrating an example of a client deviceobtaining its location coordinates, compressing the coordinates, andtransmitting the compressed coordinates to the wireless communicationsdevice in the communication system shown in FIG. 1.

FIGS. 5A and 5B illustrate the use of latitude and longitude coordinatesin identifying location, and how location resolution of longitudecoordinates varies based on latitude.

FIG. 6 is a flow chart illustrating an example of a network devicereceiving compressed client device location coordinates, decompressingthe coordinates, and providing an absolute location of the client devicein the communication system shown in FIG. 1.

FIG. 7 is a block diagram illustrating a simplified example of themethod and system for compressing location data of a radio forover-the-air transmission.

Skilled artisans will appreciate that elements in the figures areillustrated for simplicity and clarity and have not necessarily beendrawn to scale. For example, the dimensions of some of the elements inthe figures may be exaggerated relative to other elements to help toimprove understanding of embodiments of the present invention.

The method components have been represented where appropriate byconventional symbols in the drawings, showing only those specificdetails that are pertinent to understanding the embodiments of thepresent invention so as not to obscure the disclosure with details thatwill be readily apparent to those of ordinary skill in the art havingthe benefit of the description herein.

DETAILED DESCRIPTION

A method and system for compressing location data of a radio forover-the-air transmission is provided herein. In operation, a clientdevice obtains raw latitude and raw longitude coordinates reflecting acurrent location of the client device, the raw latitude coordinaterepresented by x number of bits and the raw longitude coordinaterepresented by y number of bits. The client device truncates the rawlatitude coordinate by removing n number of most significant bits fromthe raw latitude coordinate to create a compressed latitude coordinate,and truncates the raw longitude coordinate by removing m number of mostsignificant bits from the raw longitude coordinate to create acompressed longitude coordinate, where m varies as a function of thevalue of the raw latitude coordinate. The client device then wirelesslytransmits the compressed longitude and compressed latitude coordinatesto a network device for decompression and use as an indication of theclient device's absolute location.

At the network device, the compressed longitude and compressed latitudecoordinates are received from the client device, and the network deviceobtains raw latitude and raw longitude coordinates reflecting one of itscurrent location and a current location of a wireless communicationsdevice in direct communication with the client device. The networkdevice then decompresses the received compressed longitude and latitudecoordinates using the received compressed longitude and latitudecoordinates and its own determined raw latitude and longitudecoordinates.

The compressed latitude coordinates are decompressed by comparing thecompressed latitude coordinates with a sub-range of the raw latitudecoordinates of the network device and, if it is determined that thedifference is outside of a maximum wireless range of one of a wirelesscommunications device and the network device, modifying remaining mostsignificant bits of the raw latitude coordinate as a function of thedifference. Then, the remaining most significant bits of the rawlatitude coordinate, modified or unmodified, are concatenated to thecompressed latitude coordinate to create a decompressed latitudecoordinate.

The compressed longitude coordinates are decompressed by comparing thecompressed longitude coordinate with a sub-range of bits in the rawlongitude coordinates of the communication device, where the sub-rangeof bits varies as a function of the value of one the latitude coordinate(of the client device or the remote device, and, if it is determinedthat the difference is outside of a maximum wireless range of thewireless communications device, modifying remaining most significantbits of the raw longitude coordinate as a function of the difference.Then, the remaining most significant bits of the raw longitudecoordinate, modified or unmodified, are concatenated to the compressedlongitude coordinate to create a decompressed longitude coordinate.

Subsequently, the network device provides a determined absolute locationof the client device using the decompressed latitude and longitudecoordinates (to itself, or some other device in the communicationsnetwork in which it is disposed or coupled).

Various other embodiments and variances will also be discussed, in moredetail, in the following detailed description and attached figures.

I. Communication System Structure and Devices

FIG. 1 is a block diagram illustrating a communication system 100employing a method and system for compressing location data of a radiofor over-the-air transmission. The communication system 100 comprises aplurality of network devices (including a wireless communications device102 having a coverage area 104 defined by a communications range 106, aswitch/router/gateway (hereinafter, “switch”) device 110, and alocation-based services device 112), and one or more client devices 108.

The network devices, including the wireless communications device 102,switch device 110, and location-based services device 112, may be linkedvia one or more of private networks, public networks, such as theInternet, wireless networks, such as satellite and cellular networks,local area networks (LANs), wide area networks (WANs), wireless localarea networks (WLANs), telephone networks, such as the Public SwitchedTelephone Networks (PSTN), or a combination of networks. Each of theprivate networks may include one or more wired and/or wireless links.

The wireless communications device 102 may comprise, among otherpossibilities, a cellular wireless base station, a two-way radiorepeater (perhaps complying with a standard such as ETSI TS 102 361 DMRstandard and/or ETSI dPMR), an IEEE 802-based wireless access point, orother wireless communication device capable of communicating with one ormore client devices 108 within a range 106. The wireless communicationsdevice 102 provides a mechanism through which client devices 108 cancommunicate with one another and/or location-based services device 112.The wireless communications range 106 determines a coverage area 104 inwhich connections may be established between fixed or roaming clientdevices 108. Although coverage area 104 is illustrated in FIG. 1 asbeing concentrically circular in shape, the actual shape of the coveragearea 104 will vary based on environmental characteristics such as landtopography, buildings, and antenna radiation directions. Furthermore,although only one wireless communications device 102 is illustrated inFIG. 1, the disclosure is not limited to such, and other embodiments mayinclude more than one wireless communications device with coverage areasdistinct from, or overlapping with, coverage area 104. Such additionalcommunications devices may be coupled directly or indirectly withcommunications device 102 and/or location-based services device 112,perhaps through switch device 110.

Wireless communications device 102 may be equipped with a locationdetermination module, such as a global positioning system (GPS)receiver, and may be configured to share its position with switch device110 and/or location-based services device 112.

Client devices 108 may take the form of a mobile or a fixed terminal.For example, the client devices 108 may comprise, among otherpossibilities, a cellular phone, a two-way radio, and an IEEE 802-basedwireless node, etc. Client devices are also equipped with a locationdetermination module, such as a GPS receiver, and may be configured toshare their position with other client devices or perhaps withlocation-based services device 112. Location data may be shared withother network devices or client devices upon request or at periodicintervals. For example, client devices 108 may be used by an emergencyservices group, and location data may be shared amongst members of thegroup so that any one member in the group can know the location of allothers in the group. As another example, location data may be sharedwith location-based services device 112 to obtain geographicallyrelevant information, such as nearby restaurants or hospitals. Otherexamples exist as well.

Switch device 110 may be any communications device configured to linkthe wireless communications device 102 (and thus client devices 108)with location-based services device 112, and may include, for example, aswitch, a router, a gateway, etc. For example, the switch device may bea mobile switching center (MSC) in a cellular network or a zonecontroller in a two-way radio network, among other possibilities. Switchdevice 110 may also be equipped with a location determination module,such as a GPS receiver.

In order to reduce consumption of communications system resources duringthe transmission of location data, client devices 108 are configured toobtain their location in the form of latitude and longitude coordinates,and to compress the coordinates prior to transmission to the networkdevices of FIG. 1. As a result of the compression, the compressedlatitude and longitude coordinates are no longer sufficient to identifyan absolute location of the client device and/or may identify a regionso large as to be unuseful in identifying a location of the clientdevice. A network device such as the wireless communications device 102may decompress the compressed coordinates, and obtain decompressedlatitude and longitude coordinates sufficient to again identify anabsolute location of the client device, by itself, or may forward thecompressed coordinates, perhaps along with its own compressed ordecompressed coordinates, to switch device 110 for decompression. Afterdecompression, the decompressed coordinates may be provided to anotherclient device 108 or to location-based services device 112 for furtherprocessing.

Further, it is to be understood that the communication system 100 isonly a logical representation of connections between client devices 108,wireless communications device 102, switch device 110, andlocation-based services device 112, and thus represents only onepossible arrangement of interconnected communications elements incommunications system 100. For example, the communication system 100 canbe extended to include more than two client devices, more than onewireless communications device 102 in the manner noted above, more thanone switch device 110, and/or more than one location-based servicesdevice 112.

FIG. 2 is a block diagram illustrating further detail of a computingdevice 200 that may perform the functions of the client device 108, thewireless communication device 102, and/or the switch device 110. Morespecifically, FIG. 2 sets forth an example computing structure that maybe used for each of the client device 108, the wireless communicationdevice 102, and the switch device 110. Program instructions stored in amemory of the computing device 200 may determine what role and whatfunctions the computing device 200 provides. Variations in the computingdevice unique to each of the client device 108, the wirelesscommunication device 102, and the switch device 110 will bedistinguished as necessary in the forthcoming description.

The computing device 200 may contain, among other components, aprocessor 202, a transceiver 204 including transmitter circuitry 206 andreceiver circuitry 208, an antenna 222, I/O devices 212, a programmemory 214, a buffer memory 216, one or more communication interfaces218, removable storage 220, and a location receiver 224. The computingdevice 200 is preferably an integrated unit and may contain at least allthe elements depicted in FIG. 2 as well as any other element necessaryfor computing device 200 to perform its electronic functions. Theelectronic components are interconnected by a bus 226.

The processor 202 may include one or more microprocessors,microcontrollers, DSPs, state machines, logic circuitry, or any otherdevice or devices that process information based on operational orprogramming instructions. Such operational or programming instructionsare stored in the program memory 214 and may include instructionsconsistent with the algorithms set forth in FIGS. 4 and 6, andaccompanying text, for compressing and decompressing locationcoordinates, as well as information related to the transmission ofsignals such as modulation, transmission frequency, transmissionprotocols, addressing, signal amplitude, etc. The program memory 214 maybe an IC memory chip containing any form of random access memory (RAM)and/or read only memory (ROM), a floppy disk, a compact disk (CD) ROM, ahard disk drive, a digital video disk (DVD), a flash memory card or anyother medium for storing digital information. One of ordinary skill inthe art will recognize that when the processor 202 has one or more ofits functions performed by a state machine or logic circuitry, thememory 214 containing the corresponding operational instructions may beembedded within the state machine or logic circuitry. The operationsperformed by the processor 202 and the rest of the computing device 200are described in more detail below.

The transmitter circuitry 206 and the receiver circuitry 208 enable thecomputing device 200 to respectively transmit and receive wirelesscommunication signals. In this regard, the transmitter circuitry 206 andthe receiver circuitry 208 include appropriate circuits to enablewireless transmissions. The implementations of the transmitter circuitry206 and the receiver circuitry 208 depend on the implementation of thecomputing device 200 and the devices with which it is to communicate.For example, the transmitter and receiver circuits 206, 208 may beimplemented as part of the computing device hardware and softwarearchitecture in accordance with known techniques. For example,transmitter and receiver circuits may be configured to communicate withone or more wireless communications protocols such as Bluetoothtransceiver, Wi-Fi perhaps in accordance with an IEEE 802.11 standard(e.g., 802.11a, 802.11b, 802.11g), WiMAX perhaps operating in accordancewith an IEEE 802.16 standard, global system for mobile communications(GSM) cellular, code division multiple access (CDMA), P25, ETSI TS 102361 DMR, ETSI dPMR, NXND, terrestrial trunked radio (TETRA) and/or othertypes of wireless transceivers configurable to communicate via awireless network.

One of ordinary skill in the art will recognize that most, if not all,of the functions of the transmitter or receiver circuitry 206, 208 maybe additionally or alternatively be implemented in a processor, such asthe processor 202. The buffer memory 216 may be any form of volatilememory, such as RAM, and is used for temporarily storing received ortransmit information and/or portions of the program memory 214.

The computing device 200 may also contain a variety of I/O devicesaccessible via I/O circuits 212, such as a keyboard with alpha-numerickeys, a display (e.g., LED, OELD) that displays information about therepeater or communications connected to the repeater, soft and/or hardkeys, touch screen, jog wheel, a microphone, and a speaker.

Storage 220 can be an IC (integrated circuit) memory chip containing anyform of RAM (random-access memory), a floppy disk, a CD-RW (compact diskwith read write), a hard disk drive, a DVD-RW (digital versatile discwith read write), a flash memory card, external subscriber identitymodule (SIM) card or any other medium for storing digital information.One of ordinary skill in the art will recognize that when the processor202 has one or more of its functions performed by a state machine orlogic circuitry, the storage 220 containing the correspondingoperational instructions can be embedded within the state machine orlogic circuitry, and may be accessible to the processor 202 directly, orindirectly via buffer memory 216.

The communication interface 218 includes appropriate hardware andsoftware architecture in accordance with known techniques that enablecommunication of data. Communication interfaces 218 may includeadditional wired and/or wireless interfaces for communicating with otherdevices. For example, communication interfaces 218 may be a wired linedevice such as an Ethernet transceiver, a Universal Serial Bus (USB)transceiver, or similar transceiver configurable to communicate via atwisted pair wire, a coaxial cable, a fiber-optic link or other physicalconnection to a wireline network. Such a wireline network may couple,for example, wireless communications device 102 with switch device 110,or switch device 110 with location-based services device 112, amongother possibilities.

Antenna 222 may comprise any known or developed structure for radiatingand receiving electromagnetic energy in a desired frequency rangecontaining corresponding wireless carrier frequencies for wirelesscommunicating between one or more of client devices 108, wirelesscommunications device 102, and/or switch device 110.

Location receiver 224 may comprise any known or developed circuit fordetermining a location of the computing device 200. For example,location receiver 224 may be a GPS receiver capable of providingabsolute coordinates based on reception of three or more signals fromorbiting GPS satellites. Other types of location determination methodscould be implemented in location receiver 224 as well, includingtriangulation with three or more base stations, among otherpossibilities.

II. Location Data Transmission Payloads

FIG. 3 sets forth one example of a packet format for transmittinglocation information from a client device 108, such as client device 108a or client device 108 b, to wireless communications device 102 and/orswitch device 110. Of course, other packet formats could additionally oralternatively be used, and other methods of encoding locationinformation in a transmission could additionally or alternatively beused.

Packet format 300 as shown in FIG. 3 includes standard-relatedinformation 302, 303 at bytes 1, 2, 11, and 12, format specifier field304, longitude overflow field 306, latitude overflow field 308, andrequest ID field 310 at byte 3, speed, direction, or radius value field312 at bytes 4-6, truncated longitude value field 314 at bytes 7-8, andtruncated latitude value field 316 at bytes 9-10. The example packetformat of FIG. 3 is formatted to comply with the control signaling block(CSBK) requirements of Digital Mobile Radio (DMR), as embodied inEuropean Telecommunications Standards Institute ETSI TS 102 361-1 V1.4.5(2007-12). The standard-related information 302, 303 may includeinformation required by the DMR standard, such as manufacturer featureidentification (FID), a cyclic-redundancy check (CRC), etc. Accordingly,only bytes 3-10 will discussed in detail herein.

At byte 3 of the packet format 300, format field 304 may describe thecontents of the packet (e.g., location information, speed, result codes,etc.). The longitude overflow field 306 may provide additional bits forthose instances where more than the 16 bits of longitude informationavailable in bytes 7-8 are required. For example, longitude overflowfield 306 may provide an additional 2 bits of longitude coordinates. Thelatitude overflow field 308 may provide additional bits for thoseinstances where more than the 16 bits of latitude information availablein bytes 9-10 are required. For example, latitude overflow field 308 mayprovide an additional 1 bit of latitude coordinates. The Request IDfield 310 may be used to indicate an event associated with thegeographic location update, e.g., a trigger or detection event inresponse to which the packet format 300 is being transmitted.

At bytes 4-6 of the packet format 300, a speed, direction, and/or radiusfield 312 of the client device 108 may be provided. For example, thespeed and direction values may be useful in predicting a future positionof the client device 108, and/or locations of interest along an expectedpath of the client device 108. Other uses are possible as well. In someembodiments, speed, direction, and/or radius field 312 may be removed inorder to allow for a 24-bit source ID field to be included in the packetformat 300 when sent on a non-scheduled GPS channel.

At bytes 7-8, a compressed (truncated) longitude value field 314 isprovided. Combining the 16-bits available at bytes 7-8 and the 2-bitsavailable at longitude overflow field 306, an 18-bit compressedlongitude coordinate can be transmitted in the packet format 300.

At bytes 9-10, a compressed (truncated) latitude value field 316 isprovided. Combining the 16-bits available at bytes 9-10 and the 1-bitavailable at latitude overflow field 308, a 17-bit compressed latitudecoordinate can be transmitted in the packet format 300.

The packet format 300 facilitates the compression of 32-bit longitudeand latitude coordinates into a compressed 18-bit longitude coordinateand a compressed 17-bit latitude coordinate, thereby effectivelycompressing 64 total bits of latitude/longitude information down to 35bits or less. It is important to note that the packet format 300 is justone example of a packet format that can be used to transmit compressedlocation coordinates consistent with this disclosure. Other packetformats could be used as well, including fields accommodating bothlarger and smaller compressed longitude and latitude coordinates thanthat illustrated in FIG. 3. For example, 64-bit longitude and latitudecoordinates could be compressed into perhaps 34-bit compressed latitudeand 36-bit compressed longitude coordinates, thereby effectivelycompressing 64 total bits of latitude/longitude information down to 35bits or less. Other possibilities exist as well.

The packet format 300 populated with fields 302-316 may be transmittedby client device 108 upon request and/or at periodic intervals, toeither provide its location to another client device 108 or tolocation-based services device 112, or to provide some form oflocation-based service to a user of the client device 108, among otherpossibilities. Upon receipt, wireless communications device 102 and/orswitch device 110 may retrieve the compressed longitude and latitudevalues from the packet format 300, and consistent with the remainingdisclosure, decompress the longitude and latitude values to re-create anabsolute location of the client device 108.

III. Location Data Compression and Decompression Operational Examples

FIGS. 4 and 6 set forth flowcharts illustrating methods 400 and 600 ofcompressing and decompressing obtained (compressed) latitude andlongitude coordinates consistent with the longitude and latitude systemdescribed in FIGS. 5A and 5B. Method 400 may be executed at each clientdevice 108 upon request or on a periodic or intermittent basis, andmethod 600 may be executed at one or more of wireless communicationsdevice 102 and switch device 110 in response to receiving a locationpacket, such as packet format 300, from a client device 108.

At step 402 of method 400, a client device obtains raw latitude andlongitude coordinates representing a current location of the clientdevice. In one example, the coordinates are provided by a GPS receiverin the form of 32-bit encoded longitude and latitude coordinates. Othertypes of location receivers and other encodings could be used as well.

At step 404 the raw latitude coordinate provided by a location receiveris truncated to reduce the size of the coordinate for wirelesstransmission and by creating a compressed latitude coordinate. As aresult of the reduction in size, the compressed latitude coordinate mayno longer identify a unique location on the surface of the Earth, and/ormay identify a region so large as to be unuseful in identifying alocation of the client device. FIG. 5A illustrates how latitudecoordinates 502 are used to uniquely identify a location on Earth.Specifically, latitude represents a north-south location, and it isshown on a map or globe by a series of east-west running lines(parallels) 504 that parallel the equator 506, which marks the midpointbetween the two poles, and extend all around the Earth's circumference.The North Pole 508 has a latitude of 90° N, while the South Pole (notshown) has a latitude of 90° S, with the equator marking the 0°intermediate point.

Importantly, spacing between latitude parallels, as measured on an outersurface of the earth, does not vary around the Earth. For example, thedistance 510 between adjacent latitude lines is consistent around thecircumference of the Earth, such that the distance 510 is, for example,equal to the distance 512. Because the distance 510/512 does not change,a static selection and/or number of bits from the raw latitudecoordinate generated at step 402 can be truncated to create thecompressed latitude coordinate. In other words, the selection and/ornumber of bits truncated from a raw latitude coordinate does not need tochange based on a longitudinal location of the client device (e.g., asthe client device moves east or west along the circumference of theglobe in FIG. 5A). For example, at least “n” number of most significantbits (MSBs) of the raw latitude coordinate may be truncated. As a resultof the truncation of the MSBs, the compressed latitude coordinate maymatch a plurality of latitudinal locations along the Earth, e.g., thecompressed latitude coordinate may no longer identify a unique locationon the surface of the Earth, and/or may identify a region so large as tobe unuseful in identifying a location of the client device.

Additionally, “s” number of least significant bits (LSBs) of the rawlatitude coordinate may also be truncated. As a result of the truncationof the LSBs, the compressed latitude coordinate may not provide as higha resolution of location as the original raw latitude coordinateprovided (e.g., providing a determination of a location of the clientdevice within 7.5-30 feet of its actual location using the compressedlatitude coordinate as opposed to within 3 feet using the raw latitudecoordinate). By sacrificing some resolution, the compressed latitudecoordinate can be further reduced in size. As noted earlier, “s” and “n”can be applied consistently to the raw latitude coordinate withoutvariation based on the longitudinal location of the client device.

TABLE I Resolution Range N . . . 9 10 11 . . . 25 26 27 . . .2{circumflex over ( )}N . . . 2{circumflex over ( )}9 2{circumflex over( )}10 2{circumflex over ( )}11 . . . 2{circumflex over ( )}252{circumflex over ( )}26 2{circumflex over ( )}27 . . . Distance . . .7.5 15 30 . . . 97.5 195 389 . . . Feet feet Feet Miles miles milesResolution_(Latitude)=π×Radius_(Earth)×2^((N−N) ^(Max) ⁾×FeetPerMileandRange_(Latitude)=π×Radius_(Earth)×2^((N−N) ^(Max) ⁾

where, Radius_(Earth)=3959 miles and FeetPerMile=5280.

For Table 1, N_(Max)=32, Resolution is given in feet and Range is givenin miles.

Table I illustrates the bit ranges that can be used in a compressedlatitude coordinate to provide the range and resolution indicated. Forexample, LSBs in bit positions 0-8 can be truncated and still providelatitude resolution up to 7.5 feet. Other selections of LSBs can beselected based on the contents of Table I. MSBs in bit positions 28-31can be removed prior to transmission to a network communications deviceproviding wireless communications service to the client device withoutpermanent loss of that data. This is because the MSBs removed at theclient device can be restored at the network communications device (orother upstream device) as long as the wireless range of the networkcommunications device is equal to or less than the range indicated inTable I above (for example, 389 miles if truncated bits 28-31). If therange of the network communications device is greater than half of therange indicated, the network communications device may incorrectlyrestore the MSBs for a client device transmitting location informationfrom a location that is farther from the network communications devicethan the range indicated in Table I. Other selections of latitude MSBscan be selected based on the contents of Table I.

While Table I illustrates how the truncated bit-range of a latitudinalcoordinate can be truncated for 32-bit encoded latitude values, similartables can be created for other encodings, including, for example,64-bit encoded latitude values.

Returning to FIG. 4, at step 406, the raw longitude coordinate providedby the location receiver is truncated to reduce the size of thelongitude coordinate for wireless transmission by creating a compressedlongitude coordinate. As a result of the reduction in size, thecompressed longitude coordinate may no longer identify a unique locationon the surface of the Earth, and/or may identify a region so large as tobe unuseful in identifying a location of the client device. FIG. 5Billustrates how longitude coordinates 552 are used to uniquely identifya location on Earth. Specifically, longitude represents east-westlocation, and it is shown on a map or globe by a series of north-southrunning lines 554 that all come together at the North Pole and at theSouth Pole. These lines of longitude 554 are called “meridians.” Theprime meridian is at 0°, and additional meridians progress east and westalong the circumference of the globe until they meet at the 180° mark558 on the opposite side of the Earth from the prime meridian.

In contrast to latitude parallel spacing, spacing between longitudemeridians does vary between adjacent meridians between the North andSouth Poles. For example, the distance 560 between adjacent longitudemeridians near the equator 564 is different than the distance 562between adjacent longitude meridians closer to the North Pole 566.Because the distance 560/562 does change based on latitude, a staticselection and/or number of bits from the raw longitude coordinategenerated at step 402 cannot be truncated to create compressed longitudecoordinates having consistent resolutions and ranges. In other words,the selection and/or number of bits truncated from a raw longitudecoordinate needs to change based on a latitudinal location of the clientdevice (e.g., as the client device moves north or south along thecircumference of the globe in FIG. 5B) in order to maintain a consistentresolution and range across the Earth from North Pole to South Pole, andrelative to the static latitude resolution and range.

TABLE II N 7 8 9 10 11 12 13 14 2{circumflex over ( )}N 2{circumflexover ( )}7 2{circumflex over ( )}8 2{circumflex over ( )}9 2{circumflexover ( )}10 2{circumflex over ( )}11 2{circumflex over ( )}122{circumflex over ( )}13 2{circumflex over ( )}14 Lat = 0° 4 f 8 f Lat =45° 3 f 6 f 12 f 24 f Lat = 69.30°  6 f 12 f Lat = 79.82°  6 f 12 f Lat= 83.93°  6 f 12 f Lat = 87.47°  6 f 12 f Lat = 88.73°  6 f 12 f

$\mspace{20mu}{{Resolution}_{Longitude} = {2\pi \times {Radius}_{Earth} \times {\cos\left( \frac{2\pi \times {Latitude}_{Degrees}}{360} \right)} \times 2^{({N - N_{\max}})} \times {FeetPerMile}}}$

TABLE III N 25 26 27 28 29 30 31 2{circumflex over ( )}N 2{circumflexover ( )}25 2{circumflex over ( )}26 2{circumflex over ( )}272{circumflex over ( )}28 2{circumflex over ( )}29 2{circumflex over( )}30 2{circumflex over ( )}31 Lat = 0° 194.5 mi 389 mi Lat = 45° 137.5mi 275 mi 550 mi Lat = 69.30°  68.8 mi 137.5 mi  275 mi 550 mi Lat =79.82° 68.8 mi  137.5 mi  275 mi 550 mi Lat = 83.93° 68.8 mi  137.5 mi 275 mi 550 mi Lat = 87.47° 68.8 mi  137.5 mi  275 mi 550 mi Lat = 88.73°68.8 mi  137.5 mi  275 mi

$\mspace{20mu}{{Range}_{Longitude} = {2\pi \times {Radius}_{Earth} \times {\cos\left( \frac{2\pi \times {Latitude}_{Degrees}}{360} \right)} \times 2^{({N - N_{\max}})}}}$

Tables II and III illustrate the bit ranges that can be used in acompressed longitude coordinate, as a function of latitude coordinate,to provide the range and resolution indicated.

For example, “m” number of MSBs of the raw longitude coordinate may betruncated consistent with Table III above. Table III illustrates the bitranges that can be used, as a function of the current latitudinallocation of the client device, in a compressed longitude coordinate toprovide consistent ranges and resolutions. For example, for raw latitudecoordinates between 45° and 69.30°, the MSBs 27-31 may be truncated tocreate a compressed longitude coordinate having a range of approximately275 miles and resolution of 12 feet or better. MSBs 27-31 can be removedprior to transmission to a network communications device providingwireless communications service to the client device without permanentloss of these MSBs. This is because, as with the latitude coordinates,the MSBs removed at the client device can be restored at the networkcommunications device (or other upstream device) as long as the wirelessrange of the network communications device is equal to or less than halfof the range indicated in Table III above. For raw latitude coordinatesbetween 45° and 69.30°, the network communications device can restorethe truncated MSBs, using knowledge of its own location, as long as thenetwork communications device has a wireless communications range lessthan that indicated Table III (e.g., 137.5 miles, 275 miles, and 550miles depending on the number of MSBs removed prior to transmission). Ifthe range of the network communications device is greater than the rangeindicated for the selected number of truncated MSBs, the networkcommunications device may incorrectly restore the MSBs for a clientdevice transmitting location information from a location that is fartherfrom the network communications device than the maximum range indicatedin Table III.

While Table III illustrates how the truncated bit-range of alongitudinal coordinate will change based on a current latitudinallocation of the client device for 32-bit encoded latitude and longitudevalues, similar tables can be created for other encodings, including,for example, 64-bit encoded latitude and longitude values. Whatever theprecision and encoding used, the truncation applied to the longitudecoordinates must be varied based on the current determined latitudinallocation of the client device to maintain consistency in location rangeand resolution for compressed location coordinates.

Additionally, “r” number of LSBs of the raw longitude coordinate mayalso be truncated, as indicated in Table II. As a result of thetruncation of the LSBs, the compressed longitude coordinate may notprovide as high a resolution of location as the original raw longitudecoordinate (e.g., providing a determination of a location of the clientdevice within 7.5-15 feet of its actual location using the compressedlongitude coordinate as opposed to within 3 feet using the raw longitudecoordinate). By sacrificing some resolution, the compressed longitudecoordinate can be further reduced in size. Similar to “m,” “r” must bevaried as a function of the current latitudinal location of the clientdevice in order to maintain consistency in range and resolution, asillustrated in Table II, for example, above.

Returning to FIG. 4, at step 408, the client device transmits thecompressed longitude and latitude coordinates to a network device, suchas the wireless communications device 102 and/or the switch device 110for decompression consistent with method 600 set forth in FIG. 6.

Method 600 for decompressing compressed longitude and latitudecoordinates may be executed at any one of wireless communications device102, switch device 110, and/or location-based services device 112. Anydifferences in the method 600 based on where the method is executed willbe described with respect to each of steps 602-610, below.

At step 602, the compressed longitude and latitude coordinates arereceived from the client device, where the compressed longitude andlatitude coordinates were compressed consistent with the method setforth in FIG. 4. At step 604, raw network latitude and longitudecoordinates are obtained of one or more of the devices receiving thecompressed longitude and latitude coordinates. For example, if thewireless communications device 102 is executing the method 600, it mayobtain its own raw network latitude and longitude coordinates via alocation receiver, such as location receiver 224 of FIG. 2, or it may beprovided with its location via an upstream device such as switch device110. If the switch device 110 is executing the method 600, it may obtainits own location via a location receiver 224 (assuming it is co-locatedwith wireless communications device 102, for example), or it may beprovided with raw network latitude and longitude coordinates of thewireless communications device 102 by the wireless communications device102, via a local database lookup, or perhaps via an upstream networkdevice such as location-based services device 112. Finally, if thelocation-based services device 112 is executing the method 600, it mayobtain raw network latitude and longitude coordinates from one or moreof the wireless communications device 102, the network communicationsdevice 110, or some other upstream or downstream device not illustratedin FIG. 1.

In any event, once the raw network latitude and raw network longitudecoordinates are obtained in step 604, the compressed latitude coordinateis decompressed using the raw network latitude coordinate at step 606.The decompression process involves several sub-steps in re-creating anaccurate absolute location of the client device using the obtained rawnetwork latitude coordinate. First, the received compressed latitudecoordinate is compared to a same bit range of the raw network latitudecoordinate to determine whether remaining MSBs of the raw networklatitude coordinate (e.g., those more significant bits not participatingin the comparison and equivalent to the MSB bit positions that weretruncated at the client device) should be incremented or decremented toaccurately reflect the absolute location of the client device (andre-create the truncated MSBs from the client device). This situation ismore clearly illustrated with reference to FIG. 7.

FIG. 7 is a block diagram illustrating an example a communication system700 employing a simplified example method and system for compressinglocation data of a radio for over-the-air transmission. Thecommunication system 700 comprises a wireless communications device 702having a coverage area 704 defined by a communications range 706, one ormore client devices 708, a switch device 710, and a location-basedservices device 712, all corresponding to similar device alreadydescribed with respect to FIG. 1. Simply for ease of description, shortdecimal encodings of latitude locations of respective devices areprovided in FIG. 7. For example, decimal 1390 may be representative of alatitude portion of a geographic location at 42° 3′58.68″N latitude/88°3′2.82″W longitude. Other decimal encoding values in FIG. 7 are setrelative to the 1390 decimal encoding for illustration purposes.

As shown in FIG. 7, the range 706 of the wireless communications device702 is 50 (miles, kilometers, etc.), and a decimal latitude encoding ofthe location of the wireless communications device 702 is assumed to be1390. A decimal latitude encoding of client device 708 a is assumed tobe 1370 (within the range 706) and a decimal latitude encoding of clientdevice 708 b is assumed to be 1410 (also within the range 706). Inaccordance with the compression algorithm set forth herein, each of theclient devices 708 a and 708 b compress their latitude location encodingby truncating the two most significant digits and transmitting theirrespective compressed latitude encodings (70 and 10, respectively) towireless communications device 702. While FIG. 7 illustrates wirelesscommunication device 702 forwarding the compressed latitude coordinatesto switch device 710 for decompression, in another embodiment, wirelesscommunication device 702 could decompress the compressed latitudecoordinates itself.

In any event, once switch device 710 receives the compressed latitudeencodings, it obtains a raw decimal latitude encoding (either its own orof the wireless communications device 702, depending on thecommunications system 700 structure). In this case, the raw decimallatitude encoding (reflecting the geographic location of one of thewireless communication device 702 and the switch device 710) is assumedto be 1390.

At this point in the decompression process, if the switch device 710were to simply concatenate the remaining MSBs of the raw networklatitude encoding (13) onto the compressed latitude encodings (70 and10, respectively) of the client devices 708 a and 708 b, the resultantdecompressed latitude encoding values 1370 and 1310 would not accuratelyreflect the original and proper latitude encodings of 1370 and 1410.More specifically, before concatenation, we must first determine whetherthe remaining MSBs of the raw decimal latitude encoding (13) must beincremented or decremented to accurately reflect the original and properdecimal latitude encoding values of the client devices 708 a and 708 b(prior to truncation/compression). The potential to miscalculate theoriginal decimal latitude encoding values will occur whenever thereference device (here, the wireless communications device 702) has amaximum range (here, 50) that, when added or subtracted from the rawdecimal latitude encoding (here, 1390) of the wireless communicationsdevice 702, causes the remaining MSBs (e.g., those MSBs in positionsthat were truncated at the client stations 708) of the raw decimallatitude encoding to change.

Accordingly, a mathematical operation and comparison is executed at theswitch device 710 to determine whether the remaining MSBs in the rawdecimal latitude encoding need to be incremented or decremented prior toconcatenation with the received compressed latitude encodings. In afirst comparison, if subtracting bits of the raw decimal latitudeencoding corresponding to bit positions of the received compressedlatitude encodings from the received compressed latitude encodingsresults in a number less than the negative of the maximum range, theremaining MSBs in the raw decimal latitude encoding are incrementedprior to concatenation. For client device 708 a, the mathematicaloperation and comparison amounts to 70-90<−50, which is false, suchthat, subject to a second comparison, the remaining MSBs in the rawdecimal latitude encoding may be concatenated to the compressed latitudeencoding without modification, resulting in a decompressed latitudeencoding of 1370 for client device 708 a. For client device 708 b, themathematical operation and comparison amounts to 10-90<−50, which istrue, such that the remaining MSBs in the raw decimal latitude encodingare incremented and then concatenated to the compressed latitudeencoding, resulting in a decompressed latitude encoding of 1410 forclient device 708 b.

In the second comparison, if subtracting bits of the raw decimallatitude encoding corresponding to bit positions of the receivedcompressed latitude encoding from the received compressed latitudeencoding results in a number greater than the maximum range, theremaining MSBs in the raw decimal latitude encoding are decrementedprior to concatenation. For client device 708 a, the mathematicaloperation and comparison amounts to 90-70>50, which is false, such that,since both the first and second comparisons failed, the remaining MSBsin the raw decimal latitude encoding are concatenated to the compressedlatitude encoding without modification, resulting in a decompressedlatitude of 1370 for client device 708 a.

Since the first comparison already succeeded for client device 708 b, weneed not execute the second comparison, however, since the order ofcomparisons is immaterial, we will present the second comparison forcompleteness and in the event that the second comparison is executedprior to or in parallel with the first comparison. For client device 708b, the mathematical operation and comparison amounts to 10-90>50, whichis false, such that the remaining MSBs in the raw decimal latitudeencoding are not decremented prior to concatenation to the compressedlatitude encoding, but may be (and in fact are) incremented subject tothe first comparison.

Returning to FIG. 6, once the decompressed latitude encodings areobtained at step 606, the decompressed longitude encodings are obtainedat step 608. The decompression process at step 608 is substantially thesame as that set forth above with respect to step 606, with theexception that the bit positions of the compressed longitude encodingvary based on latitude, and thus, the comparison of bits between thecompressed longitude encoding and the raw decimal longitude encodingmust take into consideration this variation. Accordingly, for examplewith reference to Table I above, for a compressed longitude encodingassociated with one of a decompressed latitude coordinate and rawnetwork latitude coordinate in the range of 45° to 69.30°, the bits ofthe compressed longitude encoding will be compared to bits 0-27 (or somesub-portion thereof depending on desired resolution and range) of theraw decimal longitude encoding to determine whether to increment ordecrement remaining MSBs (bits 28-31) in the raw decimal longitudeencoding. Alternatively, for a compressed longitude coordinateassociated with one of a decompressed latitude coordinate and rawnetwork latitude coordinate in the range of 69.30° to 79.82°, the bitsof the compressed longitude encoding will be compared to bits 0-28 (orsome sub-portion thereof depending on desired resolution and/or range)of the raw decimal longitude encoding. Similarly, and as reflected inTable I above, the number of remaining MSBs in the raw decimal longitudeencoding that will be concatenated to the compressed longitude encodingto create the decompressed longitude encoding will also vary withlatitude. For example, for a compressed longitude encoding associatedwith one of a decompressed latitude coordinate and raw network latitudecoordinate in the range of 45° to 69.30°, 4-5 MSBs of the raw decimallongitude encoding will be concatenated onto the compressed longitudeencoding (depending on desired resolution and/or range). Alternatively,for a compressed longitude encoding associated with one of adecompressed latitude coordinate and raw network latitude coordinate inthe range of 69.30° to 79.82°, 3-4 MSBs of the raw decimal longitudeencoding will be concatenated onto the compressed longitude encoding(depending on desired resolution and/or range).

At step 610, the decompressed longitude and latitude are provided,reflecting the absolute location of the client device 108 to a same, orminimally reduced, resolution compared to the original raw networklocation data generated at the client device. In some cases, for exampleabove where the latitude is encoded into a decimal or binary format, adecoding is performed to convert the encoded number into alatitude/longitude pair (in degrees, minutes, seconds, or perhaps as adecimal number to the tenth, hundredth, thousandth, or other moreprecise decimal position).

LSBs truncated in either of the compressed latitude or compressedlongitude coordinates are lost and cannot be restored via method 600(e.g., the compression is lossy). However, and as illustrated in TablesI-III and elsewhere above, a resolution of between 3 and 30 feet canstill be maintained while reducing a location transmission CSBK to asingle transmission burst. This amounts to a substantial savings innetwork bandwidth consumption when multiplied over the number of clientdevices typically transmitting location updates in a typical wirelesscommunications system.

In the foregoing specification, specific embodiments have beendescribed. However, one of ordinary skill in the art appreciates thatvarious modifications and changes can be made without departing from thescope of the invention as set forth in the claims below. Accordingly,the specification and figures are to be regarded in an illustrativerather than a restrictive sense, and all such modifications are intendedto be included within the scope of present teachings.

The benefits, advantages, solutions to problems, and any element(s) thatmay cause any benefit, advantage, or solution to occur or become morepronounced are not to be construed as a critical, required, or essentialfeatures or elements of any or all the claims. The invention is definedsolely by the appended claims including any amendments made during thependency of this application and all equivalents of those claims asissued.

Moreover in this document, relational terms such as first and second,top and bottom, and the like may be used solely to distinguish oneentity or action from another entity or action without necessarilyrequiring or implying any actual such relationship or order between suchentities or actions. The terms “comprises,” “comprising,” “has”,“having,” “includes”, “including,” “contains”, “containing” or any othervariation thereof, are intended to cover a non-exclusive inclusion, suchthat a process, method, or article that comprises, has, includes,contains a list of elements does not include only those elements but mayinclude other elements not expressly listed or inherent to such process,method, or article. An element proceeded by “comprises . . . a”, “has .. . a”, “includes . . . a”, “contains . . . a” does not, without moreconstraints, preclude the existence of additional identical elements inthe process, method, or article that comprises, has, includes, containsthe element. The terms “a” and “an” are defined as one or more unlessexplicitly stated otherwise herein. The terms “substantially”,“essentially”, “approximately”, “about” or any other version thereof,are defined as being close to as understood by one of ordinary skill inthe art, and in one non-limiting embodiment the term is defined to bewithin 10%, in another embodiment within 5%, in another embodimentwithin 1% and in another embodiment within 0.5%. The term “coupled” asused herein is defined as connected, although not necessarily directlyand not necessarily mechanically. A device or structure that is“configured” in a certain way is configured in at least that way, butmay also be configured in ways that are not listed.

It will be appreciated that some embodiments may be comprised of one ormore generic or specialized processors (or “processing devices”) such asmicroprocessors, digital signal processors, customized processors andfield programmable gate arrays (FPGAs) and unique stored programinstructions (including both software and firmware) that control the oneor more processors to implement, in conjunction with certainnon-processor circuits, some, most, or all of the functions of themethod described herein. Alternatively, some or all functions could beimplemented by a state machine that has no stored program instructions,or in one or more application specific integrated circuits (ASICs), inwhich each function or some combinations of certain of the functions areimplemented as custom logic. Of course, a combination of the twoapproaches could be used.

Moreover, an embodiment can be implemented as a computer-readablestorage medium having computer readable code stored thereon forprogramming a computer (e.g., comprising a processor) to perform amethod as described and claimed herein. Examples of suchcomputer-readable storage mediums include, but are not limited to, ahard disk, a CD-ROM, an optical storage device, a magnetic storagedevice, a ROM (Read Only Memory), a PROM (Programmable Read OnlyMemory), an EPROM (Erasable Programmable Read Only Memory), an EEPROM(Electrically Erasable Programmable Read Only Memory) and a Flashmemory. Further, it is expected that one of ordinary skill,notwithstanding possibly significant effort and many design choicesmotivated by, for example, available time, current technology, andeconomic considerations, when guided by the concepts and principlesdisclosed herein will be readily capable of generating such softwareinstructions and programs and ICs with minimal experimentation.

The Abstract of the Disclosure is provided to allow the reader toquickly ascertain the nature of the technical disclosure. It issubmitted with the understanding that it will not be used to interpretor limit the scope or meaning of the claims. In addition, in theforegoing Detailed Description, it can be seen that various features aregrouped together in various embodiments for the purpose of streamliningthe disclosure. This method of disclosure is not to be interpreted asreflecting an intention that the claimed embodiments require morefeatures than are expressly recited in each claim. Rather, as thefollowing claims reflect, inventive subject matter lies in less than allfeatures of a single disclosed embodiment. Thus the following claims arehereby incorporated into the Detailed Description, with each claimstanding on its own as a separately claimed subject matter.

We claim:
 1. A method for compressing and transmitting obtained locationdata reflecting a current location of a client device, the methodcomprising: obtaining, via the client device, raw latitude and rawlongitude coordinates reflecting a current location of the clientdevice, the raw latitude coordinate represented by x number of bits andthe raw longitude coordinate represented by y number of bits;truncating, via the client device, the raw latitude coordinate byremoving n number of most significant bits from the raw latitudecoordinate to create a compressed latitude coordinate; truncating, viathe client device, the raw longitude coordinate by removing m number ofmost significant bits from the raw longitude coordinate to create acompressed longitude coordinate, where m varies as a function of thevalue of the raw latitude coordinate; and wirelessly transmitting, viathe client device, the compressed longitude and compressed latitudecoordinates to a remote device for decompression and use as anindication of the client device's absolute location.
 2. The method ofclaim 1, wherein m is greater for lower raw latitude coordinate valuesand lower for greater raw latitude coordinate values.
 3. The method ofclaim 2, wherein m varies between 1 and
 6. 4. The method of claim 2,further comprising truncating, via the client device, the raw longitudecoordinate by removing r number of least significant bits (LSBs) fromthe raw longitude coordinate, where r varies as a function of the valueof the raw latitude coordinate and inversely with the value of m.
 5. Themethod of claim 2, wherein m decreases in a non-linear fashion as thevalue of the raw latitude coordinate increases.
 6. The method of claim1, further comprising truncating, via the client device, the rawlatitude coordinate by removing s number of least significant bits(LSBs) from the raw latitude coordinate.
 7. The method of claim 6,wherein n and s do not vary as a function of the raw latitude or rawlongitude coordinates.
 8. The method of claim 1, wherein x and y are 32,m varies between 1 and 5, and n varies between 4 and
 5. 9. The method ofclaim 8, further comprising: truncating, via the client device, the rawlongitude coordinate by removing r number of least significant bits(LSBs) from the raw longitude coordinate, where r varies as a functionof the value of the raw latitude coordinate and inversely with the valueof m; and further comprising truncating, via the client device, the rawlatitude coordinate by removing s number of LSBs from the raw latitudecoordinate; where r varies between 8 and 11 and s is
 10. 10. The methodof claim 1, wherein the compressed latitude coordinate provides alocation resolution of 15 feet and range of 195 to 389 miles, and thecompressed longitude coordinate provides a location resolution ofbetween 6 and 12 feet and a range of between 275 and 550 miles.
 11. Amethod for decompressing received compressed longitude and latitudecoordinates from a client device at a network device, the methodcomprising: wirelessly receiving, via the network device, compressedlongitude and compressed latitude coordinates from a client device;obtaining, via the network device, raw network latitude and raw networklongitude coordinates reflecting a current location of one of thenetwork device and another network device coupled to the client device;decompressing the compressed latitude coordinate received from theclient device, via the network device, by: comparing the compressedlatitude coordinate with a sub-range of the raw network latitudecoordinate and, if it is determined that the difference is outside of amaximum wireless range of the one of the network device and the anothernetwork device coupled to the client device, modifying remaining mostsignificant bits of the raw network latitude coordinate as a function ofthe difference; concatenating the remaining most significant bits of theraw network latitude coordinate, modified or unmodified, to thecompressed latitude coordinate to create a decompressed latitudecoordinate; decompressing the compressed longitude coordinate receivedfrom the client device, via the network device, by: comparing thecompressed longitude coordinate with a sub-range of bits in the rawnetwork longitude coordinate, wherein the sub-range of bits varies as afunction of the value of the one of the decompressed latitude coordinateand the raw network latitude coordinate and, if it is determined thatthe difference is outside of a maximum wireless range, modifyingremaining most significant bits of the raw network longitude coordinateas a function of the difference; concatenating the remaining mostsignificant bits of the raw network longitude coordinate, modified orunmodified, to the compressed longitude coordinate to create adecompressed longitude coordinate; providing, via the network device, adetermined absolute location of the client device using the decompressedlatitude and longitude coordinates.
 12. The method of claim 11, whereincomparing the compressed latitude coordinate with a sub-range of the rawnetwork latitude coordinate comprises comparing bits of the compressedlatitude coordinate with a same number and same position of bits in theraw network latitude coordinate; and wherein comparing the compressedlongitude coordinate with a sub-range of bits in the raw networklongitude coordinate comprises comparing all of the bits of thecompressed longitude coordinate with a same number and same position ofbits in the raw network longitude coordinate, wherein the position ofbits in the raw network longitude coordinate varies as a function of thevalue of the one of the decompressed latitude coordinate and the rawnetwork latitude coordinate.
 13. The method of claim 12, wherein theposition of bits in the raw network longitude coordinate is lower forlower raw network latitude coordinate values and greater for greater rawnetwork latitude coordinate values.
 14. The method of claim 12, whereinthe position of bits in the raw network longitude coordinate also doesnot include r number of least significant bits (LSBs) of the raw networklongitude coordinate, where r varies as a function of the value of theone of the decompressed latitude coordinate and the raw network latitudecoordinate.
 15. The method of claim 12, wherein the position of bits inthe raw network longitude coordinate varies in a non-linear fashion asthe value of the one of the decompressed latitude coordinate and the rawnetwork latitude coordinate increases.
 16. The method of claim 12,wherein comparing bits of the compressed latitude coordinate with a samenumber and same position of bits in the raw network latitude coordinatedoes not include s number of least significant bits (LSBs) from the rawnetwork latitude coordinate.
 17. The method of claim 16, wherein s doesnot vary as a function of the raw network latitude or raw networklongitude coordinates.
 18. The method of claim 12, wherein x and y are32, the remaining most significant bits of the raw network latitudecoordinate concatenated to the compressed latitude coordinate variesfrom the 4 to 5 most significant bits of the raw network latitudecoordinate, and the remaining most significant bits of the raw networklongitude coordinate concatenated to the compressed longitude coordinatevaries from the 1 to 5 most significant bits of the raw networklongitude coordinate.
 19. The method of claim 12, wherein providing thedetermined absolute location comprises transmitting the decompressedlatitude and longitude coordinates to another communications device viaone of a wired and wireless link.
 20. The method of claim 19, whereinthe another communications device is one of an emergency control centerand another client device.
 21. The method of claim 12, wherein it isdetermined that the difference between the compressed latitudecoordinate and the same number and same position of bits in the rawnetwork latitude coordinate of the network device is outside of themaximum wireless range, modifying the remaining most significant bits ofthe raw network latitude coordinate as a function of the differencecomprises: if subtracting the value of the same number and same positionof bits in the raw network latitude coordinate from the value of thecompressed latitude coordinate results in a number greater than themaximum wireless range, decrementing the remaining most significant bitsof the raw network latitude coordinate prior to concatenation with thecompressed latitude coordinate; and if subtracting the value of the samenumber and same position of bits in the raw network latitude coordinatefrom the value of the compressed latitude coordinate results in a numberless than the negative of the maximum wireless range, incrementing theremaining most significant bits of the raw network latitude coordinateprior to concatenation with the compressed latitude coordinate.
 22. Themethod of claim 12, wherein it is determined that the difference betweenthe compressed longitude coordinate and the same number and sameposition of bits in the raw network longitude coordinate of thecommunications device is outside of the maximum wireless range,modifying the remaining most significant bits of the raw networklongitude coordinate as a function of the difference comprises: ifsubtracting the value of the same number and same position of bits inthe raw network longitude coordinate from the value of the compressedlongitude coordinate results in a number greater than the maximumwireless range, decrementing the remaining most significant bits of theraw network longitude coordinate prior to concatenation with thecompressed longitude coordinate; and if subtracting the value of thesame number and same position of bits in the raw network longitudecoordinate from the value of the compressed longitude coordinate resultsin a number less than the negative of the maximum wireless range,incrementing the remaining most significant bits of the raw networklongitude coordinate prior to concatenation with the compressedlongitude coordinate.